fix missing return values on platform channels for destroyTexture

macos/Classes/SwiftPolyvoxFilamentPlugin.swift

@@ -162,6 +162,7 @@ public class SwiftPolyvoxFilamentPlugin: NSObject, FlutterPlugin, FlutterTexture
             self.flutterTextureId = nil 
             self.pixelBuffer = nil
             self.metalTexture = nil
+            result(true)
         case "resize":
             let args = call.arguments as! [Any]
             let width = UInt32(args[0] as! Int64)